Signaling of global motion relative to available reference frames

ABSTRACT

A decoder includes circuitry configured to receive a bitstream, extract a header including a list of reference frames available for motion compensation, such as global motion compensation, determine, using the header, a motion model for a current block, the motion relative to a reference frame contained in the list of reference frames, and decode the current block using the motion model. Related apparatus, systems, techniques and articles are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/006,568, filed on Aug. 28, 2020, and titled “SIGNALING OF GLOBALMOTION RELATIVE TO AVAILABLE REFERENCE FRAMES,” and issuing as U.S. Pat.No. 11,265,566 on Mar. 1, 2022, which claims the benefit of priority ofInternational Application No. PCT/US20/29942, filed on Apr. 24, 2020 andentitled “SIGNALING OF GLOBAL MOTION VECTOR IN PICTURE HEADER,” whichclaims the benefit of priority of U.S. Provisional Patent ApplicationSer. No. 62/838,517, filed on Apr. 25, 2019, and titled “SIGNALING OFGLOBALMOTION RELATIVE TO AVAILABLE REFERENCE FRAMES.” Each of U.S.application Ser. No. 17/005,568, International Application No.PCT/US20/29942 and U.S. Provisional Patent Application Ser. No.62/838,517 is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to the field of videocompression. In particular, the present invention is directed tosignaling of global motion vector relative to available referenceframes.

BACKGROUND

A video codec can include an electronic circuit or software thatcompresses or decompresses digital video. It can convert uncompressedvideo to a compressed format or vice versa. In the context of videocompression, a device that compresses video (and/or performs somefunction thereof) can typically be called an encoder, and a device thatdecompresses video (and/or performs some function thereof) can be calleda decoder.

A format of the compressed data can conform to a standard videocompression specification. The compression can be lossy in that thecompressed video lacks some information present in the original video. Aconsequence of this can include that decompressed video can have lowerquality than the original uncompressed video because there isinsufficient information to accurately reconstruct the original video.

There can be complex relationships between the video quality, the amountof data used to represent the video (e.g., determined by the bit rate),the complexity of the encoding and decoding algorithms, sensitivity todata losses and errors, ease of editing, random access, end-to-end delay(e.g., latency), and the like.

Motion compensation can include an approach to predict a video frame ora portion thereof given a reference frame, such as previous and/orfuture frames, by accounting for motion of the camera and/or objects inthe video. It can be employed in the encoding and decoding of video datafor video compression, for example in the encoding and decoding usingthe Motion Picture Experts Group (MPEG)-2 (also referred to as advancedvideo coding (AVC) and H.264) standard. Motion compensation can describea picture in terms of the transformation of a reference picture to thecurrent picture. The reference picture can be previous in time whencompared to the current picture, from the future when compared to thecurrent picture. When images can be accurately synthesized frompreviously transmitted and/or stored images, compression efficiency canbe improved.

SUMMARY OF THE DISCLOSURE

In an aspect, a decoder includes circuitry configured to receive abitstream, extract a header including a list of reference framesavailable for global motion compensation, determine, using the header, aglobal motion model for a current block, the global motion relative to areference frame contained in the list of reference frames, and decodethe current block using the global motion model.

In another aspect, a method includes receiving, by a decoder, abitstream. The method includes extracting a header including a list ofreference frames available for global motion compensation. The methodincludes determining, using the header, a global motion model for acurrent block, the global motion relative to a reference frame containedin the list of reference frames. The method includes decoding thecurrent block using the global motion model.

These and other aspects and features of non-limiting embodiments of thepresent invention will become apparent to those skilled in the art uponreview of the following description of specific non-limiting embodimentsof the invention in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, the drawings show aspectsof one or more embodiments of the invention. However, it should beunderstood that the present invention is not limited to the precisearrangements and instrumentalities shown in the drawings, wherein:

FIG. 1 is a diagram illustrating motion vectors of an example frame withglobal and local motion;

FIG. 2 is a process flow diagram according to some exampleimplementations of the current subject matter;

FIG. 3 is a system block diagram of an example decoder according to someexample implementations of the current subject matter;

FIG. 4 is a process flow diagram according to some exampleimplementations of the current subject matter;

FIG. 5 is a system block diagram of an example encoder according to someexample implementations of the current subject matter; and

FIG. 6 is a block diagram of a computing system that can be used toimplement any one or more of the methodologies disclosed herein and anyone or more portions thereof.

The drawings are not necessarily to scale and may be illustrated byphantom lines, diagrammatic representations and fragmentary views. Incertain instances, details that are not necessary for an understandingof the embodiments or that render other details difficult to perceivemay have been omitted.

DETAILED DESCRIPTION

“Global motion” in video refers to motion and/or a motion model commonto all pixels of a region, where a region may be a picture, a frame, orany portion of a picture or frame such as a block, CTU, or other subsetof contiguous pixels. Global motion may be caused by camera motion, forexample, camera panning and zooming may create motion in a frame thatmay typically affect the entire frame. Motion present in portions of avideo may be referred to as local motion. Local motion may be caused bymoving objects in a scene, such as without limitation an object movingfrom left to right in the scene. Videos may contain a combination oflocal and global motion. Some implementations of the current subjectmatter may provide for efficient approaches to communicate global motionto a decoder and use of global motion vectors in improving compressionefficiency.

FIG. 1 is a diagram illustrating motion vectors of an example frame 100with global and local motion. A frame 100 may include a number of blocksof pixels illustrated as squares, and their associated motion vectorsillustrated as arrows. Squares (e.g., blocks of pixels) with arrowspointing up and to the left indicate blocks with motion that may beconsidered to be global motion and squares with arrows pointing in otherdirections (indicated by 104) indicate blocks with local motion. In theillustrated example of FIG. 1, many of the blocks have same globalmotion. Signaling the global motion in a header, such as a pictureparameter set (PPS) or sequence parameter set (SPS), and using thesignaled global motion may reduce motion vector information needed byblocks and may result in improved prediction. Although for illustrativepurposes examples described below refer to determination and/orapplication of global or local motion vectors at a block level, globalmotion vectors may be determined and/or applied for any region of aframe and/or picture, including regions made up of multiple blocks,regions bounded by any geometric form such as without limitation regionsdefined by geometric and/or exponential coding in which one or morelines and/or curves bounding the shape may be angled and/or curved,and/or an entirety of a frame and/or picture. Although signaling isdescribed herein as being performed at a frame level and/or in a headerand/or parameter set of a frame, signaling may alternatively oradditionally be performed at a sub-picture level, where a sub-picturemay include any region of a frame and/or picture as described above.

As an example, and still referring to FIG. 1, simple translationalmotion may be described using a motion vector (MV) with two componentsMVx, MVy that describes displacement of blocks and/or pixels in acurrent frame. More complex motion such as rotation, zooming, andwarping may be described using affine motion vectors, where an “affinemotion vector,” as used in this disclosure, is a vector describing auniform displacement of a set of pixels or points represented in a videopicture and/or picture, such as a set of pixels illustrating an objectmoving across a view in a video without changing apparent shape duringmotion. Some approaches to video encoding and/or decoding may use4-parameter or 6-parameter affine models for motion compensation ininter picture coding.

For example, a six parameter affine motion may be described as:

x′=ax+by+c

y′=dx+ey+f

And a four parameter affine motion may be described as:

x′=ax+by +c

y′=−bx+ay+f

where (x,y) and (x′,y′) are pixel locations in current and referencepictures, respectively; a, b, c, d, e, and f are the parameters of theaffine motion model.

Still referring to FIG. 1, parameters used describe affine motion may besignaled to a decoder to apply affine motion compensation at thedecoder. In some approaches, motion parameters may be signaledexplicitly or by signaling translational control point motion vectors(CPMVs) and then deriving affine motion parameters from thetranslational motion vectors. Two control point motion vectors (CPMVs)may be utilized to derive affine motion parameters for a four-parameteraffine motion model and three control point translational motion vectors(CPMVs) may be utilized to obtain parameters for a six-parameter motionmodel. Signaling affine motion parameters using control point motionvectors may allow use of efficient motion vector coding methods tosignal affine motion parameters.

With continued reference to FIG. 1, some modern video compressiontechniques may use multiple reference frames in inter prediction. Whenmultiple reference frames are present, global motion relative toavailable reference frames may be signaled to more effectively applymotion compensation and improve compression efficiency. A list of framesavailable for reference may be maintained in a frame list ListO. Framesin list may be indexed by their order relative to a current frame. Allframes available for use as reference in coding a current picture may beindexed in ListO. Global motion parameters may be specified for allavailable reference frames. Presence or absence of global motionrelative to a frame in reference list may also be signaled; his mayallow for efficient signaling of global motion information.

For example, and still referring to FIG. 1, table 1 shows a new PPS withglobal motion parameters for one or more frames in reference picturelist. In the example of table 1, up to 16 reference pictures may besignaled. Presence of global motion for each available reference framemay be signaled. For all frames with global motion present, globalmotion parameters may be encoded as shown in table 1. If no predictedblocks in a current picture use global motion from a previously codedframe that is available for reference, corresponding global motionparameters may not be coded. On an encoder side this may incur framedelay if the PPS has to be updated after encoding current picture.Alternatively, efficient methods of encoding may be able to predictwhich available reference frames are not suitable for global motioncompensation and remove such frames from PPS.

TABLE 1 Descriptor pic_parameter_set_rbsp( ) {  pps_pic_parameter_set_idue(v)  pps_seq_parameter_set_id ue(v) . . . ref_pic_count u(4) for(i=1;i <= ref_pic_count; i++){  gmc_present[i] u(1) } for(i=1; i <=ref_pic_count; i++){  if(gmc_present[i])   pps_global_motion_parameters( ) }  rbsp_trailing_bits( ) }

In an embodiment, and still referring to FIG. 1, ansps_affine_enabled_flag in a PPS and/or SPS may specify whether affinemodel based motion compensation may be used for inter prediction. Ifsps_affine_enabled_flag is equal to 0, the syntax may be constrainedsuch that no affine model based motion compensation is used in the codelater video sequence (CLVS), and inter_affine_flag andcu_affine_type_flag may not be present in coding unit syntax of theCLVS. Otherwise (sps_affine_enabled_flag is equal to 1), affine modelbased motion compensation can be used in the CLVS.

Continuing to refer to FIG. 1, sps_affine_type_flag in a PPS and/or SPSmay specify whether 6-parameter affine model based motion compensationmay be used for inter prediction. If sps_affine_type_flag is equal to 0,syntax may be constrained such that no 6-parameter affine model basedmotion compensation is used in the CLVS, and cu_affine_type_flag may notpresent in coding unit syntax in the CLVS. Otherwise(sps_affine_type_flag equal to 1), 6-parameter affine model based motioncompensation may be used in CLVS. When not present, the value ofsps_affine_type_flag may be inferred to be equal to 0.

Accordingly, and still referring to FIG. 1, some implementations of thecurrent subject matter may include utilizing global motion between acurrent frame and one of a number of references frames. Which referenceframe to utilize may be explicitly signaled (e.g., in a PPS). In someimplementations, if a reference frame to be utilized is not explicitlysignaled, then the reference frame to be utilized may be a frameimmediately before current frame. Such an approach may enable moreaccurate motion representation (e.g., smaller motion vector residual),and smaller pixel residual.

FIG. 2 is a process flow diagram illustrating an example process 200 ofutilizing global motion between a current frame and one of a number ofreferences frames.

At step 205, and still referring to FIG. 2, a bitstream is received by adecoder. A current block may be contained within a bitstream thatdecoder receives. Bitstream may include, for example, data found in astream of bits that is an input to a decoder when using datacompression. Bitstream may include information necessary to decode avideo. Receiving may include extracting and/or parsing a block andassociated signaling information from bit stream. In someimplementations, a current block may include a coding tree unit (CTU), acoding unit (CU), or a prediction unit (PU).

At step 210, and continuing to refer to FIG. 2, a header may beextracted. Header may include a list of reference frames available forglobal motion compensation. At step 215, a global motion model for acurrent block may be determined using the header. Global motion may berelative to a reference frame contained in list of reference frames. Atstep 220, a current block may be decoded using global motion model.

FIG. 3 is a system block diagram illustrating an example decoder 300capable of decoding a bitstream 328 utilizing global motion between acurrent frame and one of a number of references frames. Decoder 300 mayinclude an entropy decoder processor 304, an inverse quantization andinverse transformation processor 308, a deblocking filter 312, a framebuffer 316, motion compensation processor 320 and intra predictionprocessor 324.

In operation, and further referring to FIG. 3, a bit stream 328 may bereceived by decoder 300 and input to entropy decoder processor 304,which may entropy decode portions of the bit stream into quantizedcoefficients. Quantized coefficients may be provided to inversequantization and inverse transformation processor 308, which may performinverse quantization and inverse transformation to create a residualsignal, which may be added to an output of motion compensation processor320 or intra prediction processor 324 according to processing mode.Output of the motion compensation processor 320 and intra predictionprocessor 324 may include a block prediction based on a previouslydecoded block. A sum of prediction and residual may be processed bydeblocking filter 630 and stored in a frame buffer 640.

FIG. 4 is a process flow diagram illustrating an exemplary embodiment ofa process 400 of encoding a video with INSERT, according to some aspectsof disclosed herein, that may reduce encoding complexity whileincreasing compression efficiency. At step 405, a video frame mayundergo initial block segmentation, which may be accomplished forinstance using a tree-structured macro block partitioning scheme thatmay include partitioning a picture frame into CTUs and CUs. At step 410,global motion for a current block may be determined includingdetermining a reference frame from a number of available referenceframes. At step 415, global motion information and block may be encodedand included in a bitstream. Encoded information may include an index toa list of available reference frames. Encoding may include utilizinginter prediction and intra prediction modes, for example.

FIG. 5 is a system block diagram illustrating a non-limiting example ofa video encoder 500 capable of utilizing global motion between a currentframe and one of a number of references frames. Example video encoder500 may receive an input video 504, which may be initially segmented ordividing according to a processing scheme, such as a tree-structuredmacro block partitioning scheme (e.g., quad-tree plus binary tree). Anexample of a tree-structured macro block partitioning scheme may includepartitioning a picture frame into large block elements called codingtree units (CTU). In some implementations, each CTU may be furtherpartitioned one or more times into a number of sub-blocks called codingunits (CU). A final result of this portioning may include a group ofsub-blocks that may be called predictive units (PU). Transform units(TU) may also be utilized.

Still referring to FIG. 5, example video encoder 500 may include anintra prediction processor 415, a motion estimation/compensationprocessor 512 (also referred to as an inter prediction processor)capable of supporting global motion between a current frame and one of anumber of references frames, a transform/quantization processor 516, aninverse quantization/inverse transform processor 520, an in-loop filter524, a decoded picture buffer 528, and/or an entropy coding processor532. Bit stream parameters may be input to entropy coding processor 532for inclusion in an output bit stream 536.

In operation, and continuing to refer to FIG. 5, for each block of aframe of input video 504, whether to process the block via intra pictureprediction or using motion estimation/compensation may be determined.Block may be provided to intra prediction processor 508 or motionestimation/compensation processor 512. If block is to be processed viaintra prediction, intra prediction processor 508 may perform processingto output a predictor. If block is to be processed via motionestimation/compensation, motion estimation/compensation processor 512may perform a processing including using global motion between a currentframe and one of a number of references frames, if applicable.

Further referring to FIG. 5, a residual can be formed by subtractingpredictor from input video. Residual may be received bytransform/quantization processor 516, which may perform transformationprocessing (e.g., discrete cosine transform (DCT)) to producecoefficients, which may be quantized. Quantized coefficients and anyassociated signaling information may be provided to entropy codingprocessor 532 for entropy encoding and inclusion in output bit stream536. Entropy encoding processor 532 may support encoding of signalinginformation related to encoding current block. In addition, quantizedcoefficients may be provided to inverse quantization/inversetransformation processor 520, which may reproduce pixels, which may becombined with predictor and processed by in loop filter 524, an outputof which may be stored in a decoded picture buffer 528 for use by motionestimation/compensation processor 512 that is capable of utilizingglobal motion between a current frame and one of a number of referencesframes.

Still referring to FIG. 5, although a few variations have been describedin detail above, other modifications or additions are possible. Forexample, in some implementations, current blocks may include anysymmetric blocks (8×8, 16×16, 32×32, 64×64, 128×128, and the like) aswell as any asymmetric block (8×4, 16×8, and the like).

With continued reference to FIG. 5, in some implementations, a quadtreeplus binary decision tree (QTBT) may be implemented. In QTBT, at aCoding Tree Unit level, partition parameters of QTBT may be dynamicallyderived to adapt to local characteristics without transmitting anyoverhead. Subsequently, at a Coding Unit level, a joint-classifierdecision tree structure may eliminate unnecessary iterations and controlrisk of false prediction. In some implementations, LTR frame blockupdate mode may be available as an additional option available at everyleaf node of QTBT.

In some implementations, and with further reference to FIG. 5,additional syntax elements may be signaled at different hierarchy levelsof bitstream. For example, a flag may be enabled for an entire sequenceby including an enable flag coded in a Sequence Parameter Set (SPS).Further, a CTU flag may be coded at a coding tree unit (CTU) level.

It is to be noted that any one or more of the aspects and embodimentsdescribed herein may be conveniently implemented using digitalelectronic circuitry, integrated circuitry, specially designedapplication specific integrated circuits (ASICs), field programmablegate arrays (FPGAs) computer hardware, firmware, software, and/orcombinations thereof, as realized and/or implemented in one or moremachines (e.g., one or more computing devices that are utilized as auser computing device for an electronic document, one or more serverdevices, such as a document server, etc.) programmed according to theteachings of the present specification, as will be apparent to those ofordinary skill in the computer art. These various aspects or featuresmay include implementation in one or more computer programs and/orsoftware that are executable and/or interpretable on a programmablesystem including at least one programmable processor, which may bespecial or general purpose, coupled to receive data and instructionsfrom, and to transmit data and instructions to, a storage system, atleast one input device, and at least one output device. Appropriatesoftware coding may readily be prepared by skilled programmers based onthe teachings of the present disclosure, as will be apparent to those ofordinary skill in the software art. Aspects and implementationsdiscussed above employing software and/or software modules may alsoinclude appropriate hardware for assisting in the implementation of themachine executable instructions of the software and/or software module.

Such software may be a computer program product that employs amachine-readable storage medium. A machine-readable storage medium maybe any medium that is capable of storing and/or encoding a sequence ofinstructions for execution by a machine (e.g., a computing device) andthat causes the machine to perform any one of the methodologies and/orembodiments described herein. Examples of a machine-readable storagemedium include, but are not limited to, a magnetic disk, an optical disc(e.g., CD, CD-R, DVD, DVD-R, etc.), a magneto-optical disk, a read-onlymemory “ROM” device, a random access memory “RAM” device, a magneticcard, an optical card, a solid-state memory device, an EPROM, an EEPROM,Programmable Logic Devices (PLDs), and/or any combinations thereof. Amachine-readable medium, as used herein, is intended to include a singlemedium as well as a collection of physically separate media, such as,for example, a collection of compact discs or one or more hard diskdrives in combination with a computer memory. As used herein, amachine-readable storage medium does not include transitory forms ofsignal transmission.

Such software may also include information (e.g., data) carried as adata signal on a data carrier, such as a carrier wave. For example,machine-executable information may be included as a data-carrying signalembodied in a data carrier in which the signal encodes a sequence ofinstruction, or portion thereof, for execution by a machine (e.g., acomputing device) and any related information (e.g., data structures anddata) that causes the machine to perform any one of the methodologiesand/or embodiments described herein.

Examples of a computing device include, but are not limited to, anelectronic book reading device, a computer workstation, a terminalcomputer, a server computer, a handheld device (e.g., a tablet computer,a smartphone, etc.), a web appliance, a network router, a networkswitch, a network bridge, any machine capable of executing a sequence ofinstructions that specify an action to be taken by that machine, and anycombinations thereof. In one example, a computing device may includeand/or be included in a kiosk.

FIG. 6 shows a diagrammatic representation of one embodiment of acomputing device in the exemplary form of a computer system 600 withinwhich a set of instructions for causing a control system to perform anyone or more of the aspects and/or methodologies of the presentdisclosure may be executed. It is also contemplated that multiplecomputing devices may be utilized to implement a specially configuredset of instructions for causing one or more of the devices to performany one or more of the aspects and/or methodologies of the presentdisclosure. Computer system 600 includes a processor 604 and a memory608 that communicate with each other, and with other components, via abus 612. Bus 612 may include any of several types of bus structuresincluding, but not limited to, a memory bus, a memory controller, aperipheral bus, a local bus, and any combinations thereof, using any ofa variety of bus architectures.

Memory 608 may include various components (e.g., machine-readable media)including, but not limited to, a random-access memory component, a readonly component, and any combinations thereof. In one example, a basicinput/output system 616 (BIOS), including basic routines that help totransfer information between elements within computer system 600, suchas during start-up, may be stored in memory 608. Memory 608 may alsoinclude (e.g., stored on one or more machine-readable media)instructions (e.g., software) 620 embodying any one or more of theaspects and/or methodologies of the present disclosure. In anotherexample, memory 608 may further include any number of program modulesincluding, but not limited to, an operating system, one or moreapplication programs, other program modules, program data, and anycombinations thereof.

Computer system 600 may also include a storage device 624. Examples of astorage device (e.g., storage device 624) include, but are not limitedto, a hard disk drive, a magnetic disk drive, an optical disc drive incombination with an optical medium, a solid-state memory device, and anycombinations thereof. Storage device 624 may be connected to bus 612 byan appropriate interface (not shown). Example interfaces include, butare not limited to, SCSI, advanced technology attachment (ATA), serialATA, universal serial bus (USB), IEEE 1394 (FIREWIRE), and anycombinations thereof. In one example, storage device 624 (or one or morecomponents thereof) may be removably interfaced with computer system 600(e.g., via an external port connector (not shown)). Particularly,storage device 624 and an associated machine-readable medium 628 mayprovide nonvolatile and/or volatile storage of machine-readableinstructions, data structures, program modules, and/or other data forcomputer system 600. In one example, software 620 may reside, completelyor partially, within machine-readable medium 628. In another example,software 620 may reside, completely or partially, within processor 604.

Computer system 600 may also include an input device 632. In oneexample, a user of computer system 600 may enter commands and/or otherinformation into computer system 600 via input device 632. Examples ofan input device 632 include, but are not limited to, an alpha-numericinput device (e.g., a keyboard), a pointing device, a joystick, agamepad, an audio input device (e.g., a microphone, a voice responsesystem, etc.), a cursor control device (e.g., a mouse), a touchpad, anoptical scanner, a video capture device (e.g., a still camera, a videocamera), a touchscreen, and any combinations thereof. Input device 632may be interfaced to bus 612 via any of a variety of interfaces (notshown) including, but not limited to, a serial interface, a parallelinterface, a game port, a USB interface, a FIREWIRE interface, a directinterface to bus 612, and any combinations thereof. Input device 632 mayinclude a touch screen interface that may be a part of or separate fromdisplay 636, discussed further below. Input device 632 may be utilizedas a user selection device for selecting one or more graphicalrepresentations in a graphical interface as described above.

A user may also input commands and/or other information to computersystem 600 via storage device 624 (e.g., a removable disk drive, a flashdrive, etc.) and/or network interface device 640. A network interfacedevice, such as network interface device 640, may be utilized forconnecting computer system 600 to one or more of a variety of networks,such as network 644, and one or more remote devices 648 connectedthereto. Examples of a network interface device include, but are notlimited to, a network interface card (e.g., a mobile network interfacecard, a LAN card), a modem, and any combination thereof. Examples of anetwork include, but are not limited to, a wide area network (e.g., theInternet, an enterprise network), a local area network (e.g., a networkassociated with an office, a building, a campus or other relativelysmall geographic space), a telephone network, a data network associatedwith a telephone/voice provider (e.g., a mobile communications providerdata and/or voice network), a direct connection between two computingdevices, and any combinations thereof. A network, such as network 644,may employ a wired and/or a wireless mode of communication. In general,any network topology may be used. Information (e.g., data, software 620,etc.) may be communicated to and/or from computer system 600 via networkinterface device 640.

Computer system 600 may further include a video display adapter 652 forcommunicating a displayable image to a display device, such as displaydevice 636. Examples of a display device include, but are not limitedto, a liquid crystal display (LCD), a cathode ray tube (CRT), a plasmadisplay, a light emitting diode (LED) display, and any combinationsthereof. Display adapter 652 and display device 636 may be utilized incombination with processor 604 to provide graphical representations ofaspects of the present disclosure. In addition to a display device,computer system 600 may include one or more other peripheral outputdevices including, but not limited to, an audio speaker, a printer, andany combinations thereof. Such peripheral output devices may beconnected to bus 612 via a peripheral interface 656. Examples of aperipheral interface include, but are not limited to, a serial port, aUSB connection, a FIREWIRE connection, a parallel connection, and anycombinations thereof.

The foregoing has been a detailed description of illustrativeembodiments of the invention. Various modifications and additions can bemade without departing from the spirit and scope of this invention.Features of each of the various embodiments described above may becombined with features of other described embodiments as appropriate inorder to provide a multiplicity of feature combinations in associatednew embodiments. Furthermore, while the foregoing describes a number ofseparate embodiments, what has been described herein is merelyillustrative of the application of the principles of the presentinvention. Additionally, although particular methods herein may beillustrated and/or described as being performed in a specific order, theordering is highly variable within ordinary skill to achieve embodimentsas disclosed herein. Accordingly, this description is meant to be takenonly by way of example, and not to otherwise limit the scope of thisinvention.

In the descriptions above and in the claims, phrases such as “at leastone of” or “one or more of” may occur followed by a conjunctive list ofelements or features. The term “and/or” may also occur in a list of twoor more elements or features. Unless otherwise implicitly or explicitlycontradicted by the context in which it is used, such a phrase isintended to mean any of the listed elements or features individually orany of the recited elements or features in combination with any of theother recited elements or features. For example, the phrases “at leastone of A and B;” “one or more of A and B;” and “A and/or B” are eachintended to mean “A alone, B alone, or A and B together.” A similarinterpretation is also intended for lists including three or more items.For example, the phrases “at least one of A, B, and C;” “one or more ofA, B, and C;” and “A, B, and/or C” are each intended to mean “A alone, Balone, C alone, A and B together, A and C together, B and C together, orA and B and C together.” In addition, use of the term “based on,” aboveand in the claims is intended to mean, “based at least in part on,” suchthat an unrecited feature or element is also permissible.

The subject matter described herein can be embodied in systems,apparatus, methods, and/or articles depending on the desiredconfiguration. The implementations set forth in the foregoingdescription do not represent all implementations consistent with thesubject matter described herein. Instead, they are merely some examplesconsistent with aspects related to the described subject matter.Although a few variations have been described in detail above, othermodifications or additions are possible. In particular, further featuresand/or variations can be provided in addition to those set forth herein.For example, the implementations described above can be directed tovarious combinations and sub-combinations of the disclosed featuresand/or combinations and sub-combinations of several further featuresdisclosed above. In addition, the logic flows depicted in theaccompanying figures and/or described herein do not necessarily requirethe particular order shown, or sequential order, to achieve desirableresults. Other implementations may be within the scope of the followingclaims.

What is claimed is:
 1. A decoder, the decoder comprising circuitryconfigured to: receive a bitstream including a coded current picture,the coded current picture including multiple coding tree units, eachcoding tree unit including one or more coding units; construct, usingthe bitstream, a list of stored previously decoded pictures for use asreference pictures for motion compensation prediction for the codedcurrent picture, wherein none of the stored reference pictures isobtained by pixel interpolation of a decoded picture using mappingparameters; for a current coding unit in the current picture, detectfrom header information in the bitstream for the current coding unit, aflag indicating motion compensation prediction is enabled for thecurrent coding unit, thereby indicating that each motion vector of thecurrent coding unit is determined relative to a reference picture in thelist based on a motion vector of an adjacent coding unit; if motioncompensation prediction is enabled for the current coding unit,determine based on the header of the current coding unit if a motionmodel for the current coding unit is translational motion, 4-parameteraffine motion or 6-parameter affine motion; determine at least a motionvector based on an adjacent coding unit, wherein: if the motion model ofthe current coding unit is translational motion, determining the atleast a motion vector further comprises determining a translationalmotion vector from the motion vector of an adjacent coding unit, anddecode the current coding unit using the translational motion vector; ifthe motion model of the current coding unit is 4-parameter affinemotion, determining the at least a motion vector further comprisesdetermining two control point motion vectors from the motion vectors ofadjacent coding units, and decode the current coding unit using the twocontrol point motion vectors; and if the motion model of the currentcoding unit is 6-parameter affine motion, determining the at least amotion vector further comprises determining three control point motionvectors from the motion vectors of adjacent coding units, and decode thecoding unit using the three control point motion vectors.
 2. The decoderof claim 1, where the reference frames are indexed in the list by anorder relative to a current frame.
 3. The decoder of claim 1, whereinthe header includes a picture parameter set or a sequence parameter set.4. The decoder of claim 1, wherein the header includes a flagcharacterizing whether global motion is present for the current block.5. The decoder of claim 1, wherein the global motion model includes atranslational motion model.
 6. The decoder of claim 1, wherein theglobal motion model includes a four-parameter affine motion model. 7.The decoder of claim 1, wherein the global motion model includes asix-parameter affine motion model.
 8. The decoder of claim 1, furthercomprising: an entropy decoder processor configured to receive the bitstream and decode the bitstream into quantized coefficients; an inversequantization and inverse transformation processor configured to processthe quantized coefficients including performing an inverse discretecosine; a deblocking filter; a frame buffer; and an intra predictionprocessor.
 9. The decoder of claim 1 wherein the current picturecontains a plurality of 128×128 coding tree units.
 10. The decoder ofclaim 9 wherein one of the coding tree units has a coding unit with ageometric partition.
 11. A method, the method comprising: receiving, bya decoder, a bit stream including a coded current picture, the codedcurrent picture including multiple coding tree units, each coding treeunit including one or more coding units; constructing, using thebitstream, a list of stored previously decoded pictures for use asreference pictures for motion compensation prediction for the codedcurrent picture; for a current coding unit in the current picture,detecting from header information in the bitstream for the currentcoding unit, a flag indicating motion compensation prediction is enabledfor the current coding unit, thereby indicating that each motion vectorof the current coding unit is determined relative to a reference picturein the list based on a motion vector of an adjacent coding unit; ifmotion compensation prediction is enabled for the current coding unit;determining based on the header of the current coding unit if a motionmodel for the current coding unit is translational motion, 4-parameteraffine motion or 6-parameter affine motion; determining at least amotion vector based on an adjacent coding unit, wherein: if the motionmodel of the current coding unit is translational motion, determiningthe at least a motion vector further comprises determining atranslational motion vector from the motion vector of an adjacent codingunit, and decode the current coding unit using the translational motionvector; if the motion model of the current coding unit is 4-parameteraffine motion, determining the at least a motion vector furthercomprises determining two control point motion vectors from the motionvectors of adjacent coding units, and decode the current coding unitusing the two control point motion vectors; and if the motion model ofthe current coding unit is 6-parameter affine motion, determining the atleast a motion vector further comprises determining three control pointmotion vectors from the motion vectors of adjacent coding units, anddecode the coding unit using the three control point motion vectors. 12.The method of claim 11, where the reference frames are indexed in thelist by an order relative to a current frame.
 13. The method of claim11, wherein the header includes a picture parameter set (PPS) or asequence parameter set (SPS).
 14. The method of claim 11, wherein theheader includes a flag characterizing whether global motion is presentfor the current block.
 15. The method of claim 11, wherein the globalmotion model includes a translational motion model.
 16. The method ofclaim 11, wherein the global motion model includes a four-parameteraffine motion model.
 17. The method of claim 11, wherein the globalmotion model includes a six-parameter affine motion model.
 18. Themethod of claim 11, the decoder further comprising: an entropy decoderprocessor configured to receive the bit stream and decode the bitstreaminto quantized coefficients; an inverse quantization and inversetransformation processor configured to process the quantizedcoefficients including performing an inverse discrete cosine; adeblocking filter; a frame buffer; and an intra prediction processor.19. The method of claim 11 wherein the current picture contains aplurality of 128×128 coding tree units.
 20. The method of claim 19wherein one of the coding tree units has a coding unit with a geometricpartition.